Nova (1974–…): Season 47, Episode 2 - Dog Tales - full transcript

A look at dog domestication, how scientists test wolf intelligence and decode canine DNA, and what science says about a dog's love for humans.

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This planet is home
to over a billion dogs.

So in the U.S.A., there's
more than 75 million dogs alone.

They're everywhere now.

They are really special animals.

Pickles!

They're more than just
great pets...

That's my girl.

Mm, love you, too.

Dogs have helped
make humans better hunters.

Better farmers.

They protect people from danger.



And might even save them
from themselves.

You can hug your dog.

The dogs change so many of them.

It's amazing.

What makes dogs so special?

Discoveries in genetics
and behavioral science

are now starting
to unlock their secrets.

The last decade in dog science

has been the most exciting
there's ever been.

This is just
the most amazing time

to be a dog scientist.

Where did they come from?

How did they evolve
from wild beast

to lapdog?



Fox behavior looks like dog.

It's impossible not love them.

How can dogs look so different,

yet still be dogs?

What lies behind
a dog's affection for humans?

Are dogs living with us
because we feed them,

or are they living with us
because they love us?

And could the answer

finally explain our species'
enduring friendship?

I feel that we've cracked
the puzzle of domestication.

"Dog Tales."

Right now, on "NOVA."

Humanity's best friend:

the dog.

They come
in all shapes and sizes.

But whatever the breed,

a pooch can make you feel
like a million bucks.

Hug.

Good girl.

They bring me so much

happiness and companionship.

I would dive
in front of traffic for her.

I would do anything for her.

Dogs and humans.

We're the best duo
in all of evolutionary history.

It's humanity's oldest friend.

The roots of our relationship

have long been a mystery.

But now, scientists are making
extraordinary breakthroughs.

Y'all let me know when she's
ready, and I'll start.

They're coming to the conclusion

that the bond
between our species

runs even deeper
than we thought.

And might explain
how these once-wild animals

became humanity's
perfect partner.

It's easy to love dogs.

That's my girl.

Mm, love you, too.

But how do they feel
about humans?

It certainly looks like love,

but could they just be in it
for the food?

Seems like an impossible
question to answer.

We can't ask them,
but could we read their minds?

Here in Atlanta,
a unique experiment is underway.

Kaylin is visiting
Emory University.

Good girl, all righty.

Good morning!

Hey!

Hey, Kaylin.

Good to see you.

She's part of a special project

run by Gregory Berns.

I know.

Okay, yeah, so are we
going to do some work today?

He's attempting to resolve
the biggest question about dogs.

The party line would say

that dogs, in some way,
are scam artists.

That in fact the only reason
that they live with us

is because we feed them
and because we provide shelter.

She is ready.

So the core of this project
is the questions

are dogs living with us
because we feed them

or are they living with us
because they love us?

And to me, that's all
the difference in the world.

To understand just what a dog
is thinking,

Gregory has trained them to lie
in a brain-imaging MRI machine.

Good girl, okay.

You know, the traditional ways

to understand
what dogs are thinking

is to look at their behavior.

But the problem with that

is that dogs will often
do things we don't expect.

Brain imaging gets
around these problems

by going directly to the brain,
and, in essence,

bypassing behavior
and go directly to the organ

that causes everything
to happen.

The dogs in the study

are trained to relate toys
to different outcomes.

When they see a pink car,
the dogs learn to expect praise.

When it sees a blue knight,

it learns to expect
some sausage.

By comparing
those two conditions...

the anticipation,
in particular...

to food versus human,

we can go in and look at
the reward system of the brain

and see which one is higher
or not,

or they equal, perhaps?

The level of pleasure
the dog experiences

is determined by the amount
of the neurotransmitter dopamine

the brain releases,

revealed on the scan
by increased blood flow

to specific regions.

Good girl... stay.

So, Laurie,

if you want to fade out of view,
and then we'll do the toys.

Gregory has conducted
this experiment

on numerous dogs.

And the scans are a revelation.

So, these colored areas
represent what dogs' brains do

when they're anticipating food.

It actually isn't showing
very much happening,

which means that on average,
the dogs probably

didn't care as much
about the food as we thought.

But, when expecting praise...

The dopamine levels
are regularly higher.

Now we actually do see
quite a bit of activity.

What that speaks to
is the fact that praise

is very interesting to the dogs.

Did they get one?

That was a good job!

The brain scans show
unambiguously

that most dogs love praise
just as much as food.

And some dogs
love praise even more.

Good girl.

Who's a good girl?

You are.

These results show
that a social bond

is as strong as the food that
we're providing to the dogs,

and that it's intrinsically
rewarding in and of itself.

And, to me, that's
about as close as you can say

that a dog loves you.

They are really special animals.

Our relationship from
a species-to-species level

just seems to be so amazing
and enmeshed.

So some may ask,

"How did humans
ever come to find

"an animal that seems
perfectly fit for us?

How did they ever come
to exist?"

The answer
to this canine mystery

lies in the distant past,

with an animal not known
for friendliness.

The wolf.

Folklore is filled with tales
of these frightening predators.

Even today, a wolf's eerie howl
can freeze blood.

Yet genetic research
has revealed that all dogs

originally evolved
from the gray wolf...

An animal that has roamed

the breadth
of the Northern Hemisphere

for at least 300,000 years.

The gray wolf may look
like a modern dog,

but it's
a very different creature...

an apex predator...

And ruthless carnivore

with a bone-splintering bite.

So how did that...

Give rise to this?

At the Royal Belgian Institute
of Natural Sciences,

paleontologist Mietje Germonpré

oversees a collection
of Ice Age wolf bones.

So, I have here a skull
of a typical wild wolf.

So, it's a big skull,
it's from a big animal.

And what is very special
is this long, elongated snout.

Now, I will show you
a skull of a modern dog.

So, you see immediately

that the snout
is much shorter and wider.

The relative proportions
of the skulls of wolves and dogs

are markedly different.

But in 2008,

Mietje made
an intriguing discovery.

She was studying
a 30,000-year-old wolf skull

called the Goyet skull,

named after the cave
it had been excavated from

in the 19th century.

At that time,
the discoverers thought

it was the skull of a wolf.

But I was not very happy
with that

because it looked different
to me.

Mietje's careful measurements

backed up her hunch.

This was no ordinary wolf.

This skull is clearly smaller

than the skull of wild wolves.

The snout is wider and shorter.

More comparable to the skull
of the modern dogs.

The shape of the wolf skull

seemed to be halfway
between a wolf and a modern dog:

a proto-dog.

The Goyet skull was not unique.

Hunting through
other European collections,

Mietje uncovered
more dog-like wolf skulls,

also around 30,000 years old.

Could these strange-shaped
European wolves

be the ancestors of modern dogs?

Bones alone
cannot answer that question.

Scientists would need
a much more precise tool.

Oxford University is home to
the PalaeoBarn DNA laboratory.

Greger Larson
is the lead researcher.

We are trying

to establish a pattern
through time and space

of the different
genetic signatures

that dog populations
and wolf populations have had

across the world over
the last 20,000 to 30,000 years.

Thanks to recent advances
in sampling technology,

forensic DNA examinations

can now be conducted
on prehistoric bone...

Allowing them to compare

Mietje's 30,000-year-old
specimens

to modern dog DNA.

If dog domestication took place
30,000 years ago,

and there was an unbroken line
between those dogs

and the dogs
that we currently have

sleeping on our sofas,

then you would expect

that the genetics of those dogs
30,000 years ago

would match
the modern populations.

But the limited
genetic information that we have

from the canids that would be
dogs from 30,000 years ago

doesn't match modern dogs
at all.

Mietje's 30,000-year-old
European proto-dogs

appear to have left
no descendants.

But Greger's team
also tested samples

from nearly 100 other
prehistoric canids.

And in this data,
they have found

the earliest known ancestors
of modern dogs.

Between 12,000
and 15,000 or 16,000 years ago,

we do find specimens
that are starting to possess

genetic signatures
that match those

that we find
in modern populations.

But it isn't as simple
as a single ancestral line.

They found several
spread across Eurasia.

So it looks like, within dogs,

we have three geographically
partitioned populations

that are differentiated
genetically and geographically.

The three ancestral
dog populations

and Mietje's extinct proto-dogs

do, however,
share one thing in common,

something that may give a clue

to how dogs appeared
in the first place:

They were all found at sites

associated
with another creature...

humans.

Archaeological evidence
shows that 40,000 years ago,

modern humans began moving
into Northern Eurasia,

replacing the Neanderthals
who came before them,

and apparently initiating
a transformation

in the wolves they encountered.

Really, something is,
was going on there.

Once modern humans
arrived in Europe,

we see that the wolf remains
start to change.

The evidence suggests
dog-like wolves

may have appeared several times
over the thousands of years

since people arrived,

always in places
where wolves and humans

shared hunting grounds.

The formation
of a close relationship

between people and wolves

led to dogs,
because that's what dogs are.

They are an emergent property
of a very close relationship

between wolf populations
and human populations.

But how did it happen?

How does a wild animal
become a domesticated pet?

The answer may be found
not with lifeless bones,

but with the help of one of the
wolf's distant living relatives,

the fox.

Almost 2,000 miles
east of Moscow lies the location

of a unique experiment
in domestication.

On this isolated farm,

Russian scientists
have been breeding foxes

for more than 60 years.

Their aim has been
to better understand

the effect of human contact
on wild animals.

Today, the foxes
are being inspected

by scientists
Anastasiya Kharlamova

and Daria Shepeleva.

The experiment starts

with a population
of untamed silver foxes.

Each one is subjected
to a simple test

of human toleration.

To understand the reaction
of animals toward human,

we need to open the door
and try to,

try to put our hand
inside the cage.

Ooh.

They are testing the strength

of each fox's adrenal
fight-or-flight response.

He afraid,

but he demonstrates
the aggressive reaction.

The level of reaction depends

on the size of the individual
animal's adrenal gland.

Within a population,

there is always
a range of responses.

This fox is calm,
without any aggressive sounds.

I can touch it,
and the fox doesn't bite me.

But this one demonstrate
more fear reaction

without aggressive reaction.

She demonstrate some interest
in moving toward me.

How each fox responds
determines its future.

Once a year, the foxes are bred.

Around five to 20%
of the most extreme

of both tolerant
and intolerant foxes

are chosen
to seed new populations.

After just ten generations
of this selective breeding,

the results are obvious
and dramatic.

This shed contains foxes
bred for intolerance.

All of them are
extremely aggressive.

This one will try to bite me.

The experimenters
have discovered

that they can create animals
that are dangerously antisocial.

But they have also discovered

that if you breed foxes
for tolerance,

something quite remarkable
happens.

There is population selected
for tame behavior.

And the result is,
the behavior looks like dog.

Zolotoi!

Zolotoi!

Their adrenal reaction
is markedly subdued.

They are now as relaxed
in human company

as a household pet.

All of them love people.

Love all people.

They even wag their tails.

It's impossible not love them.

The experiment suggests

that by selecting
for human toleration,

in just a few generations,

a wild animal
can be made to behave

just like a domestic animal.

But that's not all.

We select our foxes only
for behavior,

but it's interesting
that after the selection,

we have a lot
of morphological changes.

Such as...

For example, a lot of white
in her fur color.

This fox has a white nose,
white belly, white legs,

and white necks.

Some foxes even develop
curly tails.

Curly tails and white patches

are both often seen
in other domesticated animals.

What's great about
that experiment is

that what it demonstrates is

that by a continued
very strong selection

for a behavioral trait,

that you can then get
an increase in frequency

of a wide range of other traits

that were not being
selected for at all.

What that suggests is that
there's a lot of linkages

between the overall
shape and size

and way in which the animal

is put together
from an anatomical perspective

and the way that it behaves.

Some believe this combination

of behavioral
and physical changes

is part
of a domestication syndrome,

probably caused
by a genetic mutation

that reduces the effect
of special neural crest cells.

During development,
these multipurpose cells

control the ultimate size
of the adrenal gland,

determining how friendly
the animal will tend to be.

But the same cells also affect
the size of the face and legs,

rigidity of the ears and tail,

and the extent of color
in the coat.

Select for friendliness,

and every other quality
can be affected, as well.

The experimental methodology
has been challenged recently,

but it's now widely accepted
that selection for behavior

can rapidly domesticate
a wild animal.

But in the journey
from wolf to dog,

who made that selection?

Most scientists now believe
it was the wolves themselves.

Wolves are
extraordinarily adaptable.

Different packs specialize

in hunting
different types of prey.

It's thought
that when humans first arrived,

some packs may have adopted
a novel survival strategy.

It's not crazy to think
that there may have been

a population of wolves
that found themselves

attracted to people
and started following people

in the same way
that other wolf populations

have started following caribou.

Rather than hunting,

these wolves would thrive
by scavenging

close to human encampments.

But only the boldest
would hang around for long.

These adventurous wolves
would breed,

and over generations,

evolve into an increasingly
human-tolerant subspecies:

the domestic dog.

Survival of the fittest

turned out to be
survival of the friendliest.

Over the last 15,000 years,
dogs have taken on

all shapes and sizes.

At this show in North Carolina,
there are dogs of every sort.

Wow.

Veterinarian Debbye Turner
is fascinated by this variety.

Hey, look at that!

That's the occupational hazard.

Domesticated dogs
have been around

for thousands of years.

And they all come
from their wolf ancestor.

And when you think about that,

that's just
absolutely incredible...

that a big old, um,
Irish wolfhound

comes from the same ancestor

that a little tiny Maltese
comes from.

So what did the first dog,

the ancestor
of all these animals,

look like?

To find out,
geneticists have been decoding

the dog family tree.

Their results show
that some lineages split away

more than 5,000 years ago,

creating descendants who today

may reflect the appearance
of the original dog.

The Japanese Akita
is one of these ancient breeds.

These dogs separated
from the genetic line

very early on.

They are called
a Spitz-type dog,

which means they have retained
many of the characteristics,

the physical characteristics,
of their wolf ancestors.

So they have
a wedge-shaped head.

They've got
these pointy pricked ears,

they have a double coat,

and the curled tail
over their backs.

Sharing the same
curly-tailed trait

is the venerable
African Basenji.

Basenji is the grandad
of ancient dogs.

However,
they're not that trainable.

They will not do obedience
tricks like other breeds.

Come back here.

And here's an example!

There's something else very
wolf-like about a Basenji.

Its yodel.

These breeds reveal much
about how dogs

may have appeared and acted

after they first transitioned
from pack hunters

to scavengers.

And provide clues
as to why they may have

first appealed to humans.

You won't see Basenjis
doing tricks.

But because of their closeness
to their wolf ancestors,

they, um, are considered

very adept hunters.

As dogs were evolving

from wolves
into truly domesticated dogs,

their traits began to change.

They were smaller,
their snout length changed,

the strength of the muscles
that support the jaw change,

even the strength and size
of their teeth.

So they lost the ability
to take down big prey.

But they didn't lose everything.

Dogs are still
the standard bearers

when it comes to detecting
things with their nose.

A dog's nose contains 50 times
the number of olfactory sensors

as a human nose,

giving them a sense of smell
100,000 times more acute.

Combined with sharp sight
and hearing,

superb stamina,
and a docile temperament,

for humans, they were
a ready-built hunting companion.

The reason why the relationship

between dogs and humans
in a hunting situation

is so perfect

is because they complement
one another.

The dogs are the chasers,

the humans are the finishers.

15,000 years ago,

the first working partnerships
were formed.

Over the following millennia,

humans would breed dogs

to take advantage
of their wolf-like abilities.

But those selections cannot
explain the extreme variety

of body shapes we see today.

Instead, the genetic studies
indicate that a sudden explosion

of diversity in shape and size

can be traced
to a breeding craze

that began in Europe
just a few hundred years ago.

The very first kennel club was
established in 1873 in England.

And it's from there that we get
the vast majority

of the varieties and the breeds
that we see today.

Kennel clubs were breeding
organizations originally meant

to preserve
local dog characteristics.

But members began to select and
share dogs with extreme traits

to an extent
never attempted before.

Geneticists have discovered

that as a result
of this intensive breeding,

the look of Western dogs
has become controlled

by just a handful
of extremely potent genes.

In a human, over 100 genes
will determine

a few inches' difference
in a person's height.

But in a dog,
just seven super-selected genes

now control the size difference

between the smallest
and the largest.

In nearly all breeds,

just one gene is responsible
for short legs.

And mutations
in just three genes

express the majority
of coat types,

from smooth...

To long-haired...

To whatever this is.

So, most dogs today
look the way they do

because of intensive
human breeding for novelty.

But people still value dogs

not just because
of how they look,

but because of what humans
can do with them.

For thousands of years,

the dog's natural instincts
were exploited

to help humans hunt, herd,
and protect.

But in the last century,
their roles have multiplied.

Dogs are amazing.

We can train them
to do a variety of tasks.

So from very simple ones
that amuse us

to very useful things.

You're not going to have a cat
at airports sniffing out drugs

or a horse telling you that
you're about to have a seizure,

but dogs are able to do this
in a way

that just vastly supersedes
any other animal,

and I think that's what
makes them special.

So what is the source of a dog's
amazing ability to learn?

Animal behaviorist Clive Wynne

is obsessed with understanding
what's going on in a dog's head.

Most psychologists study
the minds of people.

I became fascinated in the minds
of everything except people.

And so I became very interested
with dogs,

and very, very quickly,

I became totally, totally
grabbed by this amazing animal.

They're absolutely fascinating...

their minds, their intellects,
their cognition.

Zaph...

Go.

Good girl.

For many years,
scientists have believed

that dogs are great learners

because they possess
an almost unique intelligence.

One key proof was their skill
at the pointing test.

Okay, Zaph...

Oh, what a clever doggie.

What a clever doggie...
well done.

Most pet dogs most of the time
will follow a human point.

It seems quite undramatic to us
because we're used to it,

but actually, it turns out

that not very many animals
will do this.

Okay, you ready?

Even our closest primate cousin,
the chimpanzee,

will struggle with this test
of intelligence.

But are their exceptional smarts

really what makes dogs
so special?

Maybe the answer lies in
the minds of their ancestors.

In the woods
outside Vienna, Austria,

Friederike Range
is taking her wolf for a walk.

Here at the Wolf Science Center,

they're carrying out cutting-
edge research on wolf cognition.

Sit!

You're ready to go.

The center's 15 wolves have been
brought up by humans.

I know Aragorn
11 years and three months.

So I hand-raised him
and his other pack-mates.

Alongside its wolves, the center
raises a group of dogs,

giving both sets of animals

an identical amount
of human contact.

We bring up the wolves
and the dogs in the same way.

So they have
the same experience,

and this is really crucial
if you want to compare them,

and compare
their behavioral cognition.

Friederike's team conduct
identical intelligence tests

on their dogs and wolves.

We just get it there.

Yup, and now it's working.

So what we are doing here

is testing cooperative abilities
in our dogs and wolves.

For this, we have this table.

The food on the table
can only be reached

if both ends of the rope
are pulled at the same time.

So the animal must understand
that it has to cooperate

with a human partner.

This dog shows how it's done.

Waiting for the human, he
executes the task to perfection.

That was nice!

But what about a wolf?

He's actually waiting!

Perfect!

For years, it was thought wolves
were incapable

of making the cognitive leap
necessary

to work with humans.

But these experiments
are proving the opposite.

And this result is not unique.

The team's work is showing

wolves can be highly intelligent
in multiple ways.

I don't think that a dog
is smarter than a wolf.

I think most of our studies show

that actually, the wolves
are much smarter.

Wolves have even been shown to
match dogs at the pointing test.

So, despite appearances,
hanging out with humans

did not improve
the dog's raw intelligence.

This ability

is not something
that developed in dogs

during the process
of domestication.

It was already latent
in the wolves

from which all of our dogs
are descended.

Good boy, scoot forward!

If dogs are no more intelligent
than wolves...

then why is a dog
more trainable?

Some think it may all be
a matter of attitude.

For Clive,

the mindset of his pet dog
Zaphos holds a clue.

I could tell straightaway
that Zaphos wasn't smart.

She's not
a super-intelligent dog.

But there was something
remarkable about her.

And that was so obvious
once I saw it...

this ability, this capacity,
this desire

to form strong emotional bonds.

That she's always trying
to make friends.

That she's extremely loving.

And I began to wonder,
could this be the crux ability

that has made dogs
so successful?

To demonstrate his theory,
Clive uses a simple test.

It's called the circle test.

It quantifies
how socially engaged

an animal is.

The animal is placed in a room
with a human for two minutes.

An observer totals the amount
of time the animal spends

inside the circle,
near the person.

Paired with their owners,

dogs spend upwards
of 60% of their time

inside the circle.

Even with a stranger,
Zaphos stays close

for over half the time.

Dogs just seem to like people.

But wolves behave differently.

This is not a lab environment,

but the results from this
circle test are still clear.

This young woman was involved
in raising this wolf.

They've known each other

all the wolf's life.

And, uh, nonetheless,
the wolf doesn't spend

so much time inside this circle
as a dog would do.

The wolf spends even less time
with its handler

than a dog would
with a stranger.

The fact that the wolf
doesn't want to spend

as much time inside the circle
with the person

shows us
that the wolf doesn't have

that same intense level
of social connection with people

as a dog can have.

To those who know wolves well,
this is no surprise.

A dog you can usually always get
to do what you want.

The wolves could care less.

They do it as they want
to do it,

and you can work really hard
to convince them,

and sometimes,
you are successful.

But if they don't want to,
there's nothing you can do.

Dogs inherited
their intelligence

from their wolf ancestors.

But they've also evolved
a strong desire

to bond with humans

that makes them
uniquely trainable.

Yes, good girl!

Often, in working dogs,
what makes them good?

It's a partnership.
Good girl!

That dog and that human
that it cares about...

they're the unit.

The unit is the person
and the dog together.

But the dog's desire to bond
is not just the key

to incredible feats of learning.

This bond also appears
to be unusually powerful.

So much so,
that here in California,

it's being exploited

to provide a novel pathway
for human rehabilitation.

Meet Max.

Max, good job.

He's part of a groundbreaking
program using dogs

to transform the behavior
of individuals

who are a danger to society.

Ready to go in?

Max will ultimately
be a service dog.

But much of his training
takes place behind bars,

at this prison facility
in California.

He will be in the care
of long-term inmates

convicted of serious crimes,
from armed robbery to murder.

Many are repeat offenders.

Some, like Gerry Castillo,
arrived in prison

with deep-rooted
psychological struggles.

Hi, how are you?

Good, how are you?
Good.

I spent a lot of time by myself.

I had issues of, uh...

Say, uh...

Low self-esteem.

You know, low confidence.

I was antisocial.

The prison environment

only seems to make
these problems worse.

It's in a place where you don't
have feelings.

Everything is shut off.

People don't talk about emotions
unless it's anger.

Statistically,

over half of all prisoners
in the U.S.

will reoffend on release.

Some prisons seek ways
to reverse that trend.

And in this facility,
that means dogs.

One wing has been transformed
into a virtual kennel club.

The prisoners here
are each responsible for a dog.

Man and animal live together
24/7.

I got to get up
in the mornings and feed him,

and train him,
and take him out to potty,

and just care for him
the whole day.

Even if I'm having a bad day.

Just start making a big circle.

Max's time inside
will help transform him

into an elite service dog.

Just make, keep going, circle.

But it's the transformation
in the inmates

that seasoned prison staff
find most remarkable.

Leave your dog on a sit-stay.

It's amazing.

Max!

Come here!

It, it has changed
so many of them.

Good boy.

It's wonderful to see

the caring attitude
that goes to it,

the gentleness that's put forth
through and for the dogs.

You wouldn't expect
to see that on the streets.

I see it here firsthand.

Good, Gerry!

He is my friend.

You know, he makes my day.

We bonded.

He knows me better than me.

I want you guys
to sit down first

and lure them over your legs.

By getting a dog,

it's like
I'm back with a family member.

I can actually interact
with somebody

and share my feelings
with somebody.

You could hug your dog.

Max has lifted my self-esteem,

gave me a purpose

to... to do...

to do things for someone else.

They should be nice and calm.

There is mounting evidence
that even with convicts,

the profound relationship
between dog and man

can change their whole outlook
on life.

Good.

Since this program has started,

I've had six inmates
who have left on parole

and they have not come back.

They have not hurt anybody else.

They are still maintaining
their lives

on the outside.

Now let's do another
nice little jog.

This program taught them
that there's more to life

than just themselves.

Giving people
who, by some standards,

have been written off
as unlovable,

and to have them
have the opportunity

to love and be loved
unconditionally

by this amazing creature
that loves to be loved,

that is loyal,
that wants to please you...

I love the idea
of these programs.

A dog's uniquely strong desire
to bond

may be particularly beneficial
to humans.

But dogs seem quite happy
to spread the love beyond us.

What makes dogs special is,

dogs can form very strong
loving connections

to members of any other species.

Never mind other members
of their own species,

any other species.

Dogs appear to be
not just loving,

but almost indiscriminately
affectionate.

New research suggests
that this could be

partly because dogs get flooded

with the "love hormone"
oxytocin.

And the reason for that
may lie partly

with some very special genes.

Hi!

How are you?

Nice to finally meet you!

Come on in to our humble home!

Hi!
Welcome!

Okay, you ready to make
some doughnuts?

Let's cook her up, sister!
Cook her up.

Okay, you got it, girl.

16-year-old Callie Truelove
lives with Williams syndrome,

a debilitating genetic condition
affecting one in 10,000 people.

Two-thirds cups of water.

This is gorgeous water.

It's caused by alterations
in around 30 genes,

generating multiple
developmental problems

and learning challenges.

I'm going to put them
in the oven.

There ain't nothing like
Southern-style cooking.

But through it all, Callie
radiates an incredible warmth

towards the people around her.

She just loves people.

From the time she was able
to go to somebody by herself,

she's always been very friendly.

Yes, let's do it!

They're so gorgeous!

And I love each and every
single human being

on this whole entire world.

If I could just hug
all of them at once, I would,

'cause I love them so much.

Here's what you're gonna do,
you're gonna take a doughnut...

She absolutely does love every
single person that she meets.

I've pastored a church
for 20 years,

and Callie has reached
more people

just with her everyday life

than I possibly could
in a lifetime.

I think you should
have this guy.

Callie's hyper-sociability is
a side effect of her condition,

tied to changes in three genes,

one of which supercharges
oxytocin levels.

Mm-mm!

Mm-hmm.

We got a pet down here.

Surprisingly,
people with Williams syndrome

may not be the only ones
affected by these altered genes.

This is my service dog,
Doodle Dandy.

And he's my heartbeat.

He's my sunshine.

And I can't imagine my life
without him.

Good boy.

He's helped me
through a whole lot

and he's just the best dog
in the whole wide world.

And I ain't ashamed to say it.

New research suggests
that Callie and Doodle Dandy

share more than just
a friendship.

Geneticists working with Clive

have recently discovered
the same rare mutations

that cause Callie's
hyper-sociablity

are present in the dog genome.

But they are not found
in wolves,

suggesting these rare mutations
were acquired by dogs

during domestication.

What causes dogs to be
so much more sociable,

so much more socially engaged

and desiring
loving relationships

than are wolves

are due to three of the genes

that are involved
in Williams syndrome.

I feel that we've cracked
the puzzle of domestication.

We've identified
in the genetic material

what it is that makes dogs
so unique,

and makes them so special
and so successful.

More research is still needed,
but these rare mutations

may prove to be
the secret source

of the unshakable bond
between our two species.

I think that's brilliant,

because I knew
when he was little

he had my personality,

but I didn't know we shared
the same gene, almost.

So that, that is so cool.

I promise I'm always going to be
here for you no matter what...

through thick and thin.

Dogs and humans have been
on quite a journey.

A natural instinct to exploit
their new human neighbors

led wolf evolution from vicious
predator to docile companion.

Humans have tinkered with them
through selective breeding,

perfecting useful
instinctual traits

and playing with their looks.

And it seems
like somewhere along the way,

we bred in an extreme motivation
to learn extraordinary skills.

Because we bred in
the most important trait of all.

You can hug your dog...

The discovery
that dogs experience love,

that's why they're so perfect.

Are you the most beautiful dog?

That's the thing that explains

not only how dogs
became so domesticated,

but explains
why they're man's best friend

and why we've been together
for 15,000 years.

Who knows you better
than your best friend?

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